Added tail length limit to limit duration of live tailing of logs to 1 hour (#756)

* Added tail length limit to limit duration of live tailing of logs to 1 hour

* Some code refactoring suggested from PR review for live tailing duration limit

* Fixed error messages in live tailing of logs

* Fixed lint errors

pkg/querier/querier.go

@@ -22,10 +22,12 @@ import (
 
 // Config for a querier.
 type Config struct {
+	TailMaxDuration time.Duration `yaml:"tail_max_duration"`
 }
 
 // RegisterFlags register flags.
 func (cfg *Config) RegisterFlags(f *flag.FlagSet) {
+	f.DurationVar(&cfg.TailMaxDuration, "querier.tail-max-duration", 1*time.Hour, "Limit the duration for which live tailing request would be served")
 }
 
 // Querier handlers queries.
@@ -262,7 +264,7 @@ func (q *Querier) Tail(ctx context.Context, req *logproto.TailRequest) (*Tailer,
 		return q.queryDroppedStreams(ctx, req, from, to, labels)
 	}, func(connectedIngestersAddr []string) (map[string]logproto.Querier_TailClient, error) {
 		return q.tailDisconnectedIngesters(ctx, req, connectedIngestersAddr)
-	}), nil
+	}, q.cfg.TailMaxDuration), nil
 }
 
 // passed to tailer for querying dropped streams

pkg/querier/tail.go

@@ -83,12 +83,13 @@ type Tailer struct {
 	querierTailClients    map[string]logproto.Querier_TailClient // addr -> grpc clients for tailing logs from ingesters
 	querierTailClientsMtx sync.Mutex
 
-	stopped      bool
-	blocked      bool
-	blockedMtx   sync.RWMutex
-	delayFor     time.Duration
-	responseChan chan *TailResponse
-	closeErrChan chan error
+	stopped         bool
+	blocked         bool
+	blockedMtx      sync.RWMutex
+	delayFor        time.Duration
+	responseChan    chan *TailResponse
+	closeErrChan    chan error
+	tailMaxDuration time.Duration
 
 	// when tail client is slow, drop entry and store its details in droppedEntries to notify client
 	droppedEntries []droppedEntry
@@ -103,22 +104,31 @@ func (t *Tailer) readTailClients() {
 // keeps sending oldest entry to responseChan. If channel is blocked drop the entry
 // When channel is unblocked, send details of dropped entries with current entry
 func (t *Tailer) loop() {
-	ticker := time.NewTicker(checkConnectionsWithIngestersPeriod)
-	defer ticker.Stop()
+	checkConnectionTicker := time.NewTicker(checkConnectionsWithIngestersPeriod)
+	defer checkConnectionTicker.Stop()
+
+	tailMaxDurationTicker := time.NewTicker(t.tailMaxDuration)
+	defer tailMaxDurationTicker.Stop()
 
 	tailResponse := new(TailResponse)
 
 	for {
 		if t.stopped {
-			break
+			return
 		}
 
 		select {
-		case <-ticker.C:
+		case <-checkConnectionTicker.C:
 			// Try to reconnect dropped ingesters and connect to new ingesters
 			if err := t.checkIngesterConnections(); err != nil {
-				level.Error(util.Logger).Log("Error reconnecting to disconnected ingesters", fmt.Sprintf("%v", err))
+				level.Error(util.Logger).Log("msg", "Error reconnecting to disconnected ingesters", "err", err)
+			}
+		case <-tailMaxDurationTicker.C:
+			if err := t.close(); err != nil {
+				level.Error(util.Logger).Log("msg", "Error closing Tailer", "err", err)
 			}
+			t.closeErrChan <- errors.New("reached tail max duration limit")
+			return
 		default:
 		}
 
@@ -134,8 +144,8 @@ func (t *Tailer) loop() {
 					if err := t.close(); err != nil {
 						level.Error(util.Logger).Log("Error closing Tailer", fmt.Sprintf("%v", err))
 					}
-					t.closeErrChan <- errors.New("All ingesters closed the connection")
-					break
+					t.closeErrChan <- errors.New("all ingesters closed the connection")
+					return
 				}
 				time.Sleep(nextEntryWait)
 				continue
@@ -316,7 +326,7 @@ func (t *Tailer) getCloseErrorChan() <-chan error {
 
 func newTailer(delayFor time.Duration, querierTailClients map[string]logproto.Querier_TailClient,
 	queryDroppedStreams func(from, to time.Time, labels string) (iter.EntryIterator, error),
-	tailDisconnectedIngesters func([]string) (map[string]logproto.Querier_TailClient, error)) *Tailer {
+	tailDisconnectedIngesters func([]string) (map[string]logproto.Querier_TailClient, error), tailMaxDuration time.Duration) *Tailer {
 	t := Tailer{
 		openStreamIterator: iter.NewHeapIterator([]iter.EntryIterator{}, logproto.FORWARD),
 		//droppedStreamsIterator:    &droppedStreamsIterator{},
@@ -326,6 +336,7 @@ func newTailer(delayFor time.Duration, querierTailClients map[string]logproto.Qu
 		responseChan:              make(chan *TailResponse, bufferSizeForTailResponse),
 		closeErrChan:              make(chan error),
 		tailDisconnectedIngesters: tailDisconnectedIngesters,
+		tailMaxDuration:           tailMaxDuration,
 	}
 
 	t.readTailClients()